Spiraling college tuition leaves crippling student loan debt. Active-shooter drills in schoolswarn students of a real and persistent threat. And political division, the culture wars and climate change remind young Americans of the fragility of the world they are inheriting.

But some experts are debating whether another phenomenon – smartphones, tablet computers and social media – is responsible for the rising rates of depression among children and young adults.

Major depression rates among teens and young adults are rising faster than among the overall population. The authors of a 2016 study in the journal Pediatrics found that rates of major depression among children ages 12 to 17 jumped to 11.3 percent in 2014, up from 8.7 percent in 2005. Major depression among young adults also increased, but at a slower rate.

Ramin Mojtabai, the Johns Hopkins Bloomberg School of Public Health professor who completed the study, says more research is needed on the causes of rising depression rates among teens and young adults.

“One can speculate that increased use of digital devices and social media are among the contributing factors,” Mojtabai said. “There is some evidence that cyberbullying puts children and adolescents at increased risk of depression.”

San Diego State University psychologist Jean Twenge sees a direct link between how much time teens spend on smartphones and troubling signs of mental health distress.

In her 2017 book "iGen," she cited national health surveys and other statistics to argue that a generation of teens have turned to smartphones as their preferred social outlet, and teens who spend the most time on their screens are more likely to be unhappy.

"What you get is a fundamental shift in how teens spend their leisure time," Twenge told USA TODAY. "They are spending less time sleeping, less time with their friends face to face. … It is not something that happened to their parents. It is not something that happens as a world event."

Even tech pioneers have limited their children's use of digital devices over concerns about the effects of technology on the developing brain. Microsoft co-founder Bill Gates capped his kids' cellphone use, and longtime Apple CEO Steve Jobs told The New York Timesin 2010 that he did not allow his children to use the then-newly developed iPad.

High-profile investors have asked Apple this yearwhat the company is doing to combat children's device overuse and the resulting mental- and physical-health harms.

But others are skeptical about blaming smartphone use for depression in adolescents and young adults.

“People are jumping to conclusions that there has been a cultural change with the use of social media,” says Anne Glowinski, director of adolescent and child psychiatry at education and training at Washington University in St. Louis. “There’s a laundry list of things that can be impacting young people.”

Sonia Livingstone, a social psychologist at the London School of Economics and Political Science, said there's room for legitimate debate over potential harms and benefits of teens' smartphone use.

But she said several other factors that could be contributing to rising depression. Perhaps the biggest, she said, is that it's more socially acceptable for kids to talk openly about mental health.

"What we have today is a greater degree of visibility," Livingstone told USA TODAY. "It very easily looks like an epidemic in mental health problems, but 10, 15 years ago, these were shameful things that nobody mentioned."

She said teens and young adults face more pressure to achieve in school and in extracurricular activities.

"It is becoming a more competitive world, and they have to play their part," Livingstone said. "It brings competition much earlier. So it is kind of an undermining of childhood."

Varun Soni, a vice provost at the University of Southern California overseeing the office of wellness and crisis intervention, has noticed a marked difference in his conversations with college-age students over time.

A decade ago, he said,students were more apt to chat about big-picture questions such as the meaning of life, purpose and how to live an extraordinary life.

In recent years, conversations with post-millennials have taken on a more pessimistic tone. Students now talk about alack of meaning, and despondency.

Soni initially thought it was a sign that more vulnerable students were seeking counseling. But he has heard similar feedback from conversations with counterparts at other universities.

He describes it as a “mental health crisis” in higher education.

“At the root of it is a sense of disconnection,” Soni said. “These are students who are so connected online but disconnected offline. These are students that may have 1,000 friends online but struggle to make friends in real life.”

Soni believes lack of connection is not the only factor affecting young adults. He cited mounting student loan debt and the spate of mass shootings at schools and other community places.

A survey released by the American Psychological Association showed thatmass shootings are a significant source of stress for 3 out of 4 young Americans ages 15 to 21.

Members of Generation Z also are more likely than millennials or Gen Xers to report their mental health as fair or poor, the survey found.

Soni said students are more likely to feel stress over choosing a major. With tuition costs and student loan debt rising, students feel pressure to select a field that will lead to a more lucrative career.

“Students feel like they have to get it right,” Soni said. “It’s more, 'What degree do I get to pay down the debt.' That’s very stressful, especially when industries have been disrupted in amazing ways."

Mary Alvord, a psychologist and adjunct professor at George Washington University School of Medicine, created a group-therapy program that teaches resilience and social skills to students at schools in the Washington, D.C., area. She doesn’t see a simple explanation for rise in depression rates among adolescents and young adults.

“I see things as more complex,” she said. “The other part of this discussion is, we can do something about this.”

If parents are concerned about their children's time on digital devices, she said, they can limit their use before bedtime, or require them to spend more time outdoors without digital devices.

Rather than fixating on their kids' phone use, Alvord said, parents can help children build resilience, encourage them to develop friendships and provide social support.

Livingstone said kids who feel like outcasts in their class or school may find comfort in an online community that allows them to connect with like-minded peers.

"The panic about screen time is distracting people from asking thoughtful questions about what would we like our kids to do online," Livingstone said. "What would be good things to do? We want to switch the conversation away from number of hours of screen time and start focusing on the kinds of activities and how it makes us feel."